Added a check to ensure the input `text` is a string before proceeding with parsing (#22809)

Co-authored-by: -LAN- <laipz8200@outlook.com>

api/core/llm_generator/llm_generator.py

                 ),
             )
 
-            questions = output_parser.parse(cast(str, response.message.content))
+            text_content = response.message.get_text_content()
+            questions = output_parser.parse(text_content) if text_content else []
         except InvokeError:
             questions = []
         except Exception:

api/core/llm_generator/output_parser/suggested_questions_after_answer.py

             json_obj = json.loads(action_match.group(0).strip())
         else:
             json_obj = []
-
         return json_obj

api/core/model_runtime/entities/message_entities.py

         """
         return not self.content
 
+    def get_text_content(self) -> str:
+        """
+        Get text content from prompt message.
+
+        :return: Text content as string, empty string if no text content
+        """
+        if isinstance(self.content, str):
+            return self.content
+        elif isinstance(self.content, list):
+            text_parts = []
+            for item in self.content:
+                if isinstance(item, TextPromptMessageContent):
+                    text_parts.append(item.data)
+            return "".join(text_parts)
+        else:
+            return ""
+
     @field_validator("content", mode="before")
     @classmethod
     def validate_content(cls, v):

api/core/workflow/nodes/tool/tool_node.py

             elif message.type == ToolInvokeMessage.MessageType.FILE:
                 assert message.meta is not None
                 assert isinstance(message.meta, dict)
-                assert "file" in message.meta and isinstance(message.meta["file"], File)
+                # Validate that meta contains a 'file' key
+                if "file" not in message.meta:
+                    raise ToolNodeError("File message is missing 'file' key in meta")
+
+                # Validate that the file is an instance of File
+                if not isinstance(message.meta["file"], File):
+                    raise ToolNodeError(f"Expected File object but got {type(message.meta['file']).__name__}")
                 files.append(message.meta["file"])
             elif message.type == ToolInvokeMessage.MessageType.LOG:
                 assert isinstance(message.message, ToolInvokeMessage.LogMessage)